classicxref can i use this command in shortcut xr i mean i want change classicxref in to xr

Are you referring to Shortcut Keys or Command Aliases?

I wasn't aware of the CLASSICXREF command, but I liked the old one better than the current one, so I tried changing the command alias XR to call up CLASSICXREF.  In AutoCAD2016 where I am now, oddly, it didn't "take" when I did it through the ALIASEDIT command, even after it told me XR now refers to CLASSICXREF, even after I closed AutoCAD and started it again, just in case that would make the difference.  XR still brought up the XREF command.But it did work when I opened the ACAD.PGP file in a plain-text editor and changed it there.  In any drawing, type in: (findfile "acad.pgp") and it will tell you where that file is.  Change this: